X-ray radiography imaging of cargo containers and trucks for the detection of nuclear material and other contraband requires high-intensity X-ray radiation sources. The higher the source intensity at a specific source energy, the greater the amount of material the X-ray beam can penetrate and the better the contrast resolution. In current practice, the X-ray source intensity of an inspection system is typically set to the highest level allowable (referred to herein as the Output Set Point or OSP) under the particular circumstances of the system and the inspection area, and all cargo is inspected using this fixed intensity, whether the accurate inspection of the cargo requires this intensity or not. This OSP is, however, typically not the highest rated intensity that the source is capable of producing. More often than not, the OSP is set to not exceed a specified radiation dose limit at the boundary of a predefined exclusion zone, or, in case of a portal inspection system (where truck drivers drive their trucks through the inspection system), to stay below a certain dose limit to the driver of the inspected truck. There are, therefore, two deficiencies of the current practice:                1. The rated maximum intensity of the source is usually higher than the OSP and the inspection system is therefore intrinsically capable of providing higher cargo penetration than it is set to provide;        2. The system uses much higher intensity for certain cargos (or parts thereof) than needed, leading, on average, to unnecessarily high radiation levels around the inspection system.        